A 4-stroke internal combustion engine typically comprises an intake valve for drawing an air/fuel mixture into a cylinder's combustion chamber and an exhaust valve for allowing combustion byproducts to escape from the chamber. A spark plug ignites the air/fuel mixture in a cylinder to move a piston, connecting rod, and crankshaft to provide power to the engine. These components are typically controlled by an engine control unit (“ECU”), which controls, among other things, the timing of fuel injection, the amount of fuel to be injected, and the timing of the spark. The spark time can be controlled to adjust the characteristics of combustion in a cylinder, and thus the force exerted on the piston, connecting rod, and crankshaft.
U.S. Pat. No. 6,109,986 discloses an idle speed control system for a marine propulsion system. The system controls an amount of fuel injected into the combustion chamber of an engine cylinder as a function of the error between a selected target speed and an actual speed. The speed can be engine speed measured in revolutions per minute or, alternatively, it can be boat speed measured in nautical miles per hour or kilometers per hour. By comparing target speed to actual speed, the control system selects an appropriate pulse width length for the injection of fuel into the combustion chamber and regulates the speed by increasing or decreasing the pulse width.
U.S. patent application Ser. No. 14/489,075 discloses systems and methods for controlling internal combustion engines having a plurality of piston-cylinders that cause rotation of a crankshaft. A crankshaft sensor is configured to sense rotational speed of the crankshaft, and a controller is configured to calculate an acceleration for each piston-cylinder based on the rotational speed of the crankshaft and then balance the accelerations of the respective piston-cylinders by modifying a combustion input to one or more of the piston-cylinders in order to reduce engine vibration.
U.S. Pat. No. 5,701,865 discloses a method of adjusting idle spark for an individual cylinder of an internal combustion engine in an automotive vehicle, including the steps of determining crankshaft acceleration for an individual cylinder of the internal combustion engine and determining an average acceleration error for the individual cylinder based on the determined crankshaft acceleration. The method also includes the steps of determining an adaptive spark advance for the individual cylinder based on the determined average acceleration error and determining a new spark advance for the individual cylinder based on the determined adaptive spark advance and a nominal spark advance. The method further includes the steps of adjusting idle spark for the individual cylinder based on the new spark advance for the individual cylinder.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.